REGIOSELECTIVITY OF THE TELLURIUM-INDUCED CYCLISATION OF TERMINALLY SUBSTITUTED ALLYL, BUTENYL AND PROPARGYL THIOETHERS OF THIENOPYRIMIDINE

Abstract

The method of electrophilic intramolecular cyclization is widely used for the synthesis of condensed thienopyrimidine derivatives. In this work, the regioselectivity of the process of electrophilic intramolecular cyclization of terminally substituted allylic derivatives, but-1-enyl and propargyl thioethers of thienopyrimidine with p-methoxyphenyltellurttrichloride was investigated.
 It was established that as a result of the tellurium-induced cyclization of butenyl thioethers of 5,6-dimethyl-3-phenylthieno[2,3-d]pyrimidin-4(3H)-one with p-methoxyphenyltellurium trichloride, angular tricyclic chlorides ― 8-(dichloro(4-methoxyphenyl)-tellanyl)-2,3,9-trimethyl-4-oxo-5-phenyl-5,7,8,9-tetrahydro-4H-thieno[3',2':5,6]pyrimido[2,1-b][1,3]thiazine-10-ium and 9-((dichloro(4-methoxyphenyl)-tellanyl)methyl)-2,3-dimethyl-4-oxo-5-phenyl-5,7,8,9-tetrahydro-4H-thieno­[3',2':5,6]pyrimido[2,1-b][1,3]thiazine-10-ium with an annealed six-membered ring in the form of complexes with p-methoxyphenyltellurium trichloride. It was proved that the electrophilic intramolecular cyclization of 5,6-dimethyl-2-(prop-2-yn-1-ylthio)-3-phenylthieno[2,3-d]pyrimidin-4(3H)-one with aryltellurium trichloride occurs with the formation of an aryltellurium trichloride complex with angular chloride 8-((dichloro(4-methoxyphenyl)-tallanyl)methylidene)-2,3-dimethyl-4-oxo-5-phenyl-4,5,7,8-tetrahydrothiazolo[3,2-a]thieno [3,2-e]pyrimidin-9-ium in the form of one geometric isomer.
 Keywords: electrophilic heterocyclization; p-methoxyphenyltellurium trichloride; organotellurium compounds; chloride 4H-thieno[3',2':5,6]pyrimido[2,1-b][1,3]thiazine-10-ium; chloride 4H-thieno[3',2':5,6]pyrimido[2,1-b][1,3]thiazine-10-ium; chloride thiazolo[3,2-a]thieno[3,2-e]pyrimidin-9-ium.